After you've emerged your preferred DE or WM you might need to make your alt-gr button work in your WM or DE. Copy this file to your /home/user/.Xmodmap/xmodmap.se. You might want to change the key mappings (mine are swedish/finnish) so that they correspond with your own keyboard and change the .se accordingly. Run

$ xev

to obtain the key codes. Then add the following line to the top of your /home/user/.xinitrc